The present invention relates generally to devices and methods for performing venous drainage and providing cardiac arrest in cardiac bypass surgery by using an atrial isolator which drains the inferior vena cava and superior vena cava for cardiopulmonary bypass and delivers cardioplegia.
Various cardiothoracic surgeries, including coronary artery bypass grafting (CABG), heart valve repair or replacement, septal defect repair, pulmonary thrombectomy, atherectomy, aneurysm repair and correction of congenital defects, generally require cardiopulmonary bypass and cardiac arrest. In order to arrest the heart, the heart and coronary arteries must be isolated from the peripheral vascular system, so that cardioplegia solution can be infused to paralyze the heart without paralyzing the peripheral organs. Cardiopulmonary bypass can be initiated to maintain peripheral circulation of oxygenated blood, and the flow of blood and other fluids can be controlled to provide an optimum surgical environment.
In conventional CABG surgery, circulatory isolation of the heart and coronary blood vessels generally involves opening the right atrial appendage and inserting a two-staged venous cannula, as discussed by Cmolik et al., xe2x80x9cCoronary Artery Operations and Reoperations,xe2x80x9d Cardiothoracic Surgery (1992), incorporated herein by reference. An additional cannula, positioned in the coronary sinus or the ascending aorta, is used to deliver cardioplegia solution after the patient is placed on bypass. Problems associated with this approach are that an extra wound site is required for administering cardioplegia, and that a venous drainage cannula, located in the vicinity of the surgical field, may interfere with a surgeon""s operation. In minimally invasive CABG surgery, where small incisions are made in a patient""s intercostal space, thereby minimizing trauma to the chest wall from the traditional mid-sternotomy approach, circulatory isolation of the heart and great vessels generally involves insertion of multiple large catheters in either the neck, or the groin, or both to remove blood from the superior vena cava and inferior vena cava for cardiopulmonary bypass. An additional catheter is also required to deliver cardioplegia solution under fluoroscopic guidance. Problems with this procedure are that excessive catheterization and use of fluoroscopy may be associated with increased morbidity.
New devices and methods are therefore desired for isolating the heart and coronary blood vessels from the peripheral vascular system and arresting cardiac function, particularly devices which do not require multiple cannulation sites, fluoroscopy, and/or cardioplegia catheter insertion.
The present invention provides an atrial isolator having the ability to seal off the atrium by blocking the inferior vena cava, superior vena cava, and tricuspid valve, and drain venous blood to a cardiopulmonary bypass machine, said atrial isolator further having the ability to deliver retrograde cardioplegia through the coronary sinus. The atrial isolator comprises two tubular members, both having a proximal end, a distal end, and an expandable occluder mounted on the distal end. The first tubular member has a drainage port in fluid communication with a lumen. The drainage port is proximal to the expandable occluder, which is adapted to engage an opening of the superior vena cava into the right atrium. The second tubular member has two lumens. A drainage port at the distal end is in fluid communication with the first lumen, and a cardioplegia delivery port located proximal to the drainage port is in fluid communication with the second lumen. The expandable occluder is located between the drainage port and the cardioplegia delivery port, and is adapted to engage an opening of the inferior vena cava and tricuspid valve in the right atrium. The second tubular member is slidably inserted into the lumen of the first tubular member to provide for adjustable displacement between the two expandable occluders. The atrial isolator may further comprise a locking mechanism in its proximal region to lock both occluders at a fixed displacement, so that the atrial isolator can be secured within the right atrium. The proximal end of each tubular member is also adapted for attachment to a cardiopulmonary bypass machine. The atrial isolator of the present invention allows for performance of venous drainage to a cardiopulmonary bypass machine and cardiac arrest by using one cannula system, therefore, obviating the need for multiple catheters.
The present invention also provides methods for venous cannulation for cardiopulmonary bypass during various cardiothoracic surgeries, including CABG. The venous drainage is achieved by sealing the right atrium using the atrial isolator which has (1) a first tubular member comprising a lumen, a first expandable occluder mounted on the distal end, and a drainage port located proximal to the expandable occluder communicating with the lumen, and (2) a second tubular member having first and second lumens, a second expandable occluder mounted on the distal end, a drainage port located distal of the second occluder communicating with the first lumen, and a cardioplegia delivery port located proximal of the second expandable occluder, communicating with the second lumen. An incision is made in a patient""s chest wall to provide access to the superior vena cava. The distal end of the atrial isolator is then inserted into the superior vena cava and positioned within the right atrium. The first and second expandable occluders are inflated and the displacement between the two expandable occluders is adjusted so that the first expandable occluder engages an opening of the superior vena cava into the right atrium, while the second expandable occluder engages an opening of the inferior vena cava and tricuspid valve into the right atrium. In this way, blood flow to the right atrium is isolated from the peripheral vascular system. The two expandable occluders can be locked at a fixed displacement by a locking mechanism on the atrial isolator. Venous blood can be withdrawn from the superior vena cava through the drainage port of the first tubular member and from inferior vena through the drainage port of the second tubular member. Once entrance to the right atrium is sealed, cardioplegia solution can be infused through the cardioplegia delivery port into the right atrial chamber and retrograde into the coronary sinus to provide cardiac arrest.
It will be understood that there are many advantages to using an atrial isolator as disclosed herein. For example, the atrial isolator generally (1) requires only one cannulation site for its insertion, (2) does not require thoroscopy to assist in its insertion or positioning within the atrium, (3) achieves venous drainage for cardiopulmonary bypass and cardiac arrest by using one device, negating the need for multiple catheters, (4) is located away from the surgical field, therefore less likely to interfere with a surgeon""s operation, and (5) would provide a timed efficient method for venous isolation and cardioplegia delivery in a minimally invasive surgery.